U.S. patent application number 12/163329 was filed with the patent office on 2009-07-23 for contact plugs of semiconductor device and method for forming the same.
This patent application is currently assigned to HYNIX SEMICONDUCTOR INC.. Invention is credited to Yun Je CHOI.
Application Number | 20090184426 12/163329 |
Document ID | / |
Family ID | 40897602 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090184426 |
Kind Code |
A1 |
CHOI; Yun Je |
July 23, 2009 |
CONTACT PLUGS OF SEMICONDUCTOR DEVICE AND METHOD FOR FORMING THE
SAME
Abstract
The contact plugs of a semiconductor device includes first
contact plugs having an elliptical sectional shape, and second
contact plugs formed on the first contact plugs and having a
circular sectional shape. The second contact plugs being configured
to come in contact with the first contact plugs, thereby preventing
voids from being formed.
Inventors: |
CHOI; Yun Je; (Seoul,
KR) |
Correspondence
Address: |
LOWE HAUPTMAN HAM & BERNER, LLP
1700 DIAGONAL ROAD, SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
HYNIX SEMICONDUCTOR INC.
Icheon-si
KR
|
Family ID: |
40897602 |
Appl. No.: |
12/163329 |
Filed: |
June 27, 2008 |
Current U.S.
Class: |
257/773 ;
257/E21.476; 257/E23.01; 438/675 |
Current CPC
Class: |
H01L 21/76816
20130101 |
Class at
Publication: |
257/773 ;
438/675; 257/E23.01; 257/E21.476 |
International
Class: |
H01L 21/44 20060101
H01L021/44; H01L 23/48 20060101 H01L023/48 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2008 |
KR |
10-2008-0007023 |
Claims
1. A semiconductor device having a plurality of contact plugs, said
device comprising: a plurality of first contact plugs having an
elliptical sectional shape; and a plurality of second contact
plugs, each of said second contact plugs being located on a
respective first contact plug and having a circular sectional
shape.
2. The device according to claim 1, wherein a diameter of each
second contact plug is greater than a length of a minor axis of
each respective first contact plug.
3. A semiconductor device having a plurality of contact plugs, said
device comprising: a plurality of first contact plugs having an
elliptical sectional shape; and a plurality of second contact
plugs, each of said second contact plugs being located on a
respective first contact plug and having an elliptical sectional
shape which has a major axis perpendicular to a major axis of the
respective first contact plug.
4. A method for forming contact plugs of a semiconductor device,
comprising the steps of: preparing a semiconductor substrate having
a first interlayer dielectric formed thereon; forming a source
contact hole and a plurality of first drain contact holes in the
first interlayer dielectric; filling a first conductive layer in
the source contact hole and each of the first drain contact holes;
forming a second interlayer dielectric on the first interlayer
dielectric and the first conductive layer; etching the second
interlayer dielectric formed on the first conductive layer and
thereby defining second drain contact holes; and filling a second
conductive layer in the second drain contact holes.
5. The method according to claim 4, wherein the source contact hole
is defined in the form of a line, and each of the first drain
contact holes are defined to have an elliptical sectional
shape.
6. The method according to claim 4, wherein a distance between the
first drain contact holes is about 30 to 50 nm.
7. The method according to claim 4, wherein the second drain
contact holes are defined to have a circular sectional shape.
8. The method according to claim 7, wherein a diameter of each of
the second drain contact holes is greater than a length of a minor
axis of the respective first drain contact holes.
9. The method according to claim 4, wherein the step of defining
the second drain contact holes comprises the step of: exposing the
first drain contact plugs and portions of the first interlayer
dielectric; and etching the exposed portions of the first
interlayer dielectric by conducting an over-etching process.
10. The method according to claim 4, wherein the first conductive
layer and the second conductive layer are formed of tungsten
(W).
11. The method according to claim 4, wherein, before the step of
filling the first conductive layer, the method further comprises
the step of: forming spacers on sidewalls of the source contact
hole and the first drain contact holes.
12. The method according to claim 11t wherein the spacers comprise
a nitride layer.
13. The method according to claim 4, wherein, before the step of
filling the second conductive layer, the method further comprises
the step of: forming spacers on sidewalls of second drain contact
holes.
14. The method according to claim 13, wherein the spacers comprise
a nitride layer.
15. The method according to claim 4, wherein, before the step of
filling the first conductive layer, the method further comprises
the step of: forming a barrier layer on surfaces of the source
contact hole and the first drain contact holes.
16. The method according to claim 15, wherein the barrier layer
comprises a stack of a Ti layer and a TiN layer.
17. The method according to claim 4, wherein, before the step of
filling the second conductive layer, the method further comprises
the step of: forming a barrier layer on surfaces of the second
drain contact holes.
18. The method according to claim 17, wherein the barrier layer
comprises a stack of a Ti layer and a TiN layer.
19. A method for forming contact plugs of a semiconductor device,
comprising the steps of: preparing a semiconductor substrate having
a first interlayer dielectric formed thereon; forming a plurality
of first contact holes having an elliptical sectional shape, in the
first interlayer dielectric; filling a first conductive layer in
the first contact holes; forming a second interlayer dielectric on
the first interlayer dielectric and the first conductive layer;
etching portions of the second interlayer dielectric on the first
contact holes and thereby defining second contact holes having a
circular sectional shape; and filling a second conductive layer in
the second contact holes.
20. The method according to claim 19, wherein a diameter of the
circle is greater than a length of a minor axis of the ellipse.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application claims priority to Korean patent
application number 10-2008-0007023, filed on Jan. 23, 2008, which
is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the contact plugs of a
semiconductor device and a method for forming the same. More
particularly, the present invention relates to the contact plugs of
a semiconductor device, which can secure an alignment margin
thereof, and a method for forming the same.
[0003] In a semiconductor device, in order to electrically connect
a lower structure and an upper structure, contact plugs are used.
For instance, considering that the plurality of gate lines formed
on a semiconductor substrate constitute the lower structure and the
metal lines formed in layers over the gate lines constitute the
upper structure, the contact plugs electrically connect the gate
lines and the metal lines. Junction areas are formed in the
portions of the semiconductor substrate which are brought into
contact with the lower portions of the gate lines. The contact
plugs are formed between the junction areas and the upwardly
positioned metal lines and function to electrically connect them
with each other.
[0004] While the contact plugs can be formed as a single layer,
they may be formed to have a multi-layered structure depending upon
the manufacturing processes of a semiconductor device. As the
integration level of a semiconductor device increases, an aspect
ratio of contact holes increases. In this regard, when the contact
plugs are formed to have the multi-layered structure, it is
difficult to properly form a conductive layer for contact plugs.
For example, if the aspect ratio of the contact holes increases,
since the upper ends of the contact holes are likely to be closed
before the contact holes are completely filled to the bottoms
thereof, voids may be formed in the contact plugs.
[0005] If voids are formed in the contact plugs, the insides of the
contact plugs can be adversely influenced by a subsequently
conducted etching process, and the voids can serve as a factor
which increases resistance, whereby the reliability of a
semiconductor device can be degraded.
SUMMARY OF THE INVENTION
[0006] Embodiments of the present invention are directed to the
contact plugs of a semiconductor device in which first contact
plugs are first formed in a first interlayer dielectric, and after
forming a second interlayer dielectric on the first interlayer
dielectric including the first contact plugs, second contact plugs
are formed in the second interlayer dielectric to come into contact
with the first contact plugs, thereby preventing voids from being
formed in contact plugs, and a method for forming the same.
[0007] Further, the embodiments of the present invention are
directed to the contact plugs of a semiconductor device in which
first contact plugs and second contact plugs are formed to have
different widths, thereby securing an alignment margin, and a
method for forming the same.
[0008] In one aspect, contact plugs of a semiconductor device
comprises first contact plugs having an elliptical sectional shape,
and second contact plugs formed on the first contact plugs and
having the sectional shape of a circle. A diameter of the second
contact plugs is greater than a length of a minor axis of the first
contact plugs.
[0009] In another aspect of the present invention, contact plugs of
a semiconductor device comprises first contact plugs having an
elliptical sectional shape, and second contact plugs formed on the
first contact plugs and having an elliptical sectional shape which
has a major axis perpendicular to a major axis of the first contact
plugs.
[0010] In yet another aspect of the present invention, a method for
forming contact plugs of a semiconductor device comprises the steps
of preparing a semiconductor substrate having a first interlayer
dielectric formed thereon, defining a source contact hole and first
drain contact holes in the first interlayer dielectric, filling a
first conductive layer in the source contact hole and the first
drain contact holes, forming a second interlayer dielectric on the
first interlayer dielectric and the first conductive layer, etching
the second interlayer dielectric formed on the first conductive
layer and thereby defining second drain contact holes, and filling
a second conductive layer in the second drain contact holes.
[0011] The source contact hole is defined in the form of a line,
and the first drain contact holes are defined to have an elliptical
sectional shape. A distance between the first drain contact holes
is about 30 to 50 nm.
[0012] The second drain contact holes are defined to have a
circular sectional shape. A diameter of the second drain contact
holes is greater than a length of a minor axis of the first drain
contact holes.
[0013] The step of defining the second drain contact holes
comprises the step of exposing the first drain contact plugs and
portions of the first interlayer dielectric, and etching the
exposed portions of the first interlayer dielectric by conducting
an over-etching process. The first conductive layer and the second
conductive layer are formed of tungsten (W).
[0014] Before the step of filling the first conductive layer, the
method further comprises the step of forming spacers on sidewalls
of the source contact hole and the first drain contact holes.
[0015] Before the step of filling the second conductive layer, the
method further comprises the step of forming spacers on sidewalls
of second drain contact holes. The spacers comprise a nitride
layer.
[0016] Before the step of filling the first conductive layer, the
method further comprises the step of forming a barrier layer on
surfaces of the source contact hole and the first drain contact
holes.
[0017] Before the step of filling the second conductive layer, the
method further comprises the step of forming a barrier layer on
surfaces of the second drain contact holes. The barrier layer
comprises a stack of a Ti layer and a TiN layer.
[0018] In a still further aspect, a method for forming contact
plugs of a semiconductor device comprises the steps of preparing a
semiconductor substrate having a first interlayer dielectric formed
thereon, defining first contact holes having an elliptical
sectional shape, in the first interlayer dielectric, filling a
first conductive layer in the first contact holes, forming a second
interlayer dielectric on the first interlayer dielectric and the
first conductive layer, etching portions of the second interlayer
dielectric on the first contact holes and thereby defining second
contact holes having a circular sectional shape, and filling a
second conductive layer in the second contact holes. A diameter of
the circle is greater than a length of a minor axis of the
ellipse.
BRIEF DESCRIPTION OF THE DRAWINGS is
[0019] FIGS. 1A through 1D are plan views illustrating a method for
forming the contact plugs of a semiconductor device in accordance
with an embodiment of the present invention.
[0020] FIGS. 2A through 2D are sectional views explaining the
method for forming the contact plugs of a semiconductor device in
accordance with the embodiment of the present invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0021] Reference will now be made in greater detail to specific
embodiments of the invention, examples of which are illustrated in
the attached drawings. It is to be noted that the present invention
must not be construed as being limited to the following embodiments
and can be realized in a variety of ways. The embodiments are
provided to make the disclosure of the present invention complete
and to allow those persons having ordinary knowledge in the art to
better understand the scope of the present invention.
[0022] FIGS. 1A through 1D are plan views explaining a method for
forming the contact plugs of a semiconductor device in accordance
with an embodiment of the present invention, and FIGS. 2A through
2D are sectional views taken along the lines A-A' of FIGS. 1A
through 1D, explaining the method for forming the contact plugs of
a semiconductor device in accordance with the embodiment of the
present invention.
[0023] Referring to FIGS. 1A and 2A, a flash memory device will be
described by way of example.
[0024] A semiconductor substrate 100 in which an un-illustrated
lower structure (for example, including a plurality of word lines
and select lines) is formed and which includes junction areas 100a,
is prepared. In the case of a flash memory device, active regions
in a memory cell zone are formed to constitute a plurality of
strings, and an isolation layer 102 is formed between strings to
electrically insulate the active regions of the strings from each
other. Also, a plurality of word lines (not shown) are connected in
series to the respective strings, and select lines (not shown) for
transmitting a driving voltage are formed on both ends of the word
lines. A source select line (SSL) (not shown) is formed on the
source terminals of the word lines, and a drain select line (DSL)
(not shown) is formed on the drain terminals of the word lines.
[0025] A first interlayer dielectric 104 is formed on the
semiconductor substrate 100 including the above-described lower
structure. A first photoresist pattern 106, which is open in the
area of a source contact hole SCH and the areas of first drain
contact holes DCH1, is formed on the first interlayer dielectric
104. For example, the first interlayer dielectric 104 can comprise
an oxide layer and can have a thickness of 2,000.about.3,500
.ANG..
[0026] By etching the first interlayer dielectric 104 using the
first photoresist pattern 106, the portions of the junction areas
100a, which are formed on the semiconductor substrate 100, are
exposed. Therefore, the source contact hole SCH and the first drain
contact holes DCH1 are defined. At this time, it is preferred that
the source contact hole SCH be defined in the form of a line and
the first drain contact holes DCH1 be defined to have an elliptical
sectional shape in which a major axis and a minor axis have
different lengths as a matter of course. In particular, while the
distance between two first drain contact holes DCH1 adjoining each
other may vary depending upon a semiconductor device, in order to
prevent the occurrence of a bridge, the distance can be set to be
greater than 30 nm (for example, to 30 to 50 nm). Further,
un-illustrated spacers (for example, comprising a nitride layer)
can be formed on the sidewalls of the source contact hole SCH and
the first drain contact holes DCH1 so that a margin for avoiding
the occurrence of a bridge can be additionally secured. At this
time, the spacers can be formed to a thickness of about 40 to 70
.ANG..
[0027] Referring to FIGS. 1B and 2B, the first photoresist pattern
106 is removed, and a first conductive layer 108 for contact plugs
is filled in the source contact hole SCH and the first drain
contact holes DCH1. The first conductive layer 108 can be formed of
polysilicon or tungsten (W). Preferably, the first conductive layer
108 is formed of tungsten because tungsten has low resistance and a
gap-fill process can be easily conducted for tungsten.
[0028] The first conductive layer 108 for contact plugs is formed
on the first interlayer dielectric 104, preferably, to a sufficient
thickness, such that the source contact hole SCH and the first
drain contact holes DCH1 can be completely filled with the first
conductive layer 108. Then, by conducting a planarization process
(for example, a chemical mechanical polishing (CMP) process) until
the upper end of the first interlayer dielectric 104 is exposed, a
source contact line SCL and first drain contact plugs DCP1 are
formed.
[0029] Before forming the first conductive layer 108, a barrier
layer (not shown) for preventing diffusion and improving an
adhesion characteristic can be formed on the surfaces of the source
contact hole SCH and the first drain contact holes DCH1. At this
time, the barrier layer can be formed by stacking a Ti layer and a
TiN layer.
[0030] Referring to FIGS. 1C and 2C, a second interlayer dielectric
110 is formed on the first interlayer dielectric 104 and the first
conductive layer 108. The second interlayer dielectric 110 can
comprise an oxide layer and can be formed to a thickness of
2,000.about.4,000 .ANG..
[0031] A second photoresist pattern 112, which is open in the areas
of second drain contact holes DCH2, is formed on the second
interlayer dielectric 110. By etching the second interlayer
dielectric 110 using the second photoresist pattern 112, second
drain contact holes DCH2 are defined.
[0032] Specifically, it is preferred that the second drain contact
holes DCH2 be defined to have a circular sectional shape. At this
time, the second drain contact holes DCH2 are defined in a manner
such that the diameter W2 of the second drain contact holes DCH2 is
greater than the length W1 of the minor axis of the first drain
contact plugs DCP1 which are formed to have an elliptical sectional
shape, and such that the second drain contact holes DCH2 adjoining
each other do not communicate with each other. Alternatively, the
second drain contact holes DCH2 can be defined to have an
elliptical sectional shape which has a major axis perpendicular to
the major axis of the first drain contact plugs DCP1. In this case,
it may be difficult to secure a margin in the distance between
adjoining second drain contact holes DCH2. For this reason, it is
preferred that the second drain contact holes DCH2 be defined to
have a circular sectional shape as described above.
[0033] When conducting an etching process to define the second
drain contact holes DCH2, it is preferred that an over-etching
process be conducted for the exposed portions of the first
interlayer dielectric 104 such that the first drain contact plugs
DCP1 can be exposed to a sufficient extent. For example, the
over-etching process can be conducted such that the lower ends of
the second drain contact holes DCH2 are positioned at a depth of
200.about.1,000 .ANG. when measured from the upper ends of the
first drain contact plugs DCP1.
[0034] Meanwhile, spacers (not shown) for preventing the diffusion
of and improving the adhesion characteristic of a conductive layer
to be subsequently formed can be formed on the sidewalls of the
second drain contact holes DCH2. For example, the spacers can
comprise a nitride layer. A nitride layer is formed on the surfaces
of the second drain contact holes DCH2 to a thickness of about 30
to 80 .ANG.. Then, an etching process is conducted such that the
nitride layer only remains on the sidewalls of the second drain
contact holes DCH2. At this time, it is preferred that the etching
process be conducted as a dry etching process and under a pressure
of about 5 to 20 mtorr so as to reduce the loss of the spacers
which remain on the sidewalls of the second drain contact holes
DCH2.
[0035] Referring to FIGS. 1D and 2D, the second photoresist pattern
112 is removed, and a second conductive layer 114 is filled in the
second drain contact holes DCH2. The second conductive layer 114 is
formed on the second interlayer dielectric 110 having the second
drain contact holes DCH2 defined therein and on portions of the
first interlayer dielectric 104 and the first drain contact plugs
DCP1 which are exposed through the second drain contact holes DCH2.
Thereupon, a planarization process (for example, a CMP process) is
conducted until the upper end of the second interlayer dielectric
110 is exposed.
[0036] Also, before forming the second conductive layer 114, a
barrier layer can be formed on the surfaces of the second drain
contact holes DCH2 by stacking a Ti layer and a TiN layer.
[0037] In this way, second drain contact plugs DCP2, which are
electrically connected with the first drain contact plugs DCP1, are
formed. As a consequence, drain contact plugs DCP can be formed to
have the stack structure of the first drain contact plugs DCP1 and
the second drain contact plugs DCP2.
[0038] Therefore, in the present invention, when forming contact
plugs having an increased aspect ratio, the contact plugs can be
formed to have a multi-layered structure, whereby it is possible to
prevent voids from being formed in the contact plugs. In
particular, when forming the contact plugs to have the
multi-layered structure, by overlapping different sectional shapes
(for example, of an ellipse and a circle), an alignment margin can
be secured. That is to say, second contact plugs having a circular
sectional shape can be formed on the first contact plugs having an
elliptical sectional shape, or vice versa. At this time, it is
preferred that the diameter of the circle be greater than the
length of the minor axis of the ellipse.
[0039] Accordingly, the manufacturing yield can be increased in the
manufacture of a semiconductor device, and since it is possible to
prevent the electrical characteristics of a semiconductor device
from being degraded, the reliability of the semiconductor device
can be improved.
[0040] As is apparent from the above description, in the
embodiments of the present invention, first contact is plugs are
first formed in a first interlayer dielectric, and after forming a
second interlayer dielectric on the first interlayer dielectric
including the first contact plugs, second contact plugs are formed
in the second interlayer dielectric to come into contact with the
first contact plugs. Therefore, it is possible to prevent voids
from being produced in contact plugs, whereby the contact plugs can
be prevented from being damaged. Also, in the present invention,
because the first contact plugs and the second contact plugs are
formed to have different widths, an alignment margin can be
secured. As a consequence, even when an aspect ratio increases, the
contact plugs can be easily formed, whereby it is possible to
prevent the electrical characteristics of a semiconductor device
from being deteriorated, and the manufacturing yield and the
reliability of the semiconductor device can be increased and
improved.
[0041] Although specific embodiments of the present invention have
been described for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
the spirit of the invention as disclosed in the accompanying
claims.
* * * * *